The invention relates to a piezoelectric valve comprising a valve housing, which defines a valve chamber, said valve chamber containing at least one actuating member in the form of a piezoelectric flexural transducer provided, for making electrical contact with it, with at least one contact face facing an outer wall of the valve housing.
In the case of a piezoelectric valve disclosed in the European patent publication 1158182 A1 of this type the making of electrical contact with the piezoelectric flexural transducer is ensured by electrical connecting lines, which are soldered to the piezoelectric flexural transducer""s contact faces provided in the interior of the valve chamber and are also connected with electrical connection contacts, which extend through a side wall of the valve housing to the outside. These contact making measures are comparatively intricate. Moreover any electronic control circuitry desired can not be readily installed on the piezoelectric valve.
One object of the invention is thus to provide a piezoelectric valve of the type initially mentioned which more particularly as regards electrical features is so designed that it permits simpler assembly.
In order to achieve these and/or other objects appearing from the present""specification, claims and drawings, in the present invention the said outer wall of the valve housing is designed in the form of a wiring support, which possesses a support body consisting of plastic material, said body bearing, on the outer side opposite to the valve chamber, a wiring arrangement provided for electrical control of the piezoelectric flexural transducer and having electrical lines and/or electronic components, said wiring arrangement being in contact by way of at least one via, extending through a cutout in the support body, with the piezoelectric flexural transducer since such via comprises an electrically conductive elastic plug against which the at least one contact face for the piezoelectric flexural transducer is thrust at the inner side of the support body.
The wiring arrangement for the control of the piezoelectric flexural transducer is in this case, separate from the operating medium of the piezoelectric valve, outside the valve chamber and is accordingly protected against any undesired effects of the operating fluid. The electrical contact with the piezoelectric flexural transducer is performed by at least one via extending through the support body, which is in the form of an electrically conductive elastic plug assuming not only an electrically conducting function but also a contact function since it makes electrical contact by touching the contact face for the piezoelectric flexural transducer, more particularly in the interior of the valve chamber. Owing to the rubber-elastic properties of the elastic plug, against which the contact face is thrust, and the resulting return forces, there is an extremely reliable electrical connection. Furthermore the rubber-like elasticity of the elastic plug means a generous allowance for component manufacturing inaccuracies of the piezoelectric valve. Last but not least the elastic plug may also, given a suitable configuration, be in a position to provide for fluid-tight sealing of the cutout in which it is placed so that no fluid may flow through it from the interior of the valve to the outside. All in all the design in accordance with the invention provides for a relatively simple structure and economical assembly, the wiring arrangement being designed, if required, in the form of control electronic circuitry for the at least one piezoelectric flexural transducer without rendering assembly more technically involved.
Further advantageous developments of the invention are defined in the claims.
The outer wall fitted with the wiring arrangement and adapted to function as a wiring support is preferably in the form of a cover of the valve housing. During assembly there is the possibility of firstly fitting the other valve housing components with the piezoelectric flexural transducer and then performing the rest of assembly operations by simply putting on the cover.
The elastic plug is preferably an electrically conductive elastomeric or rubber body, which preferably comprises a rubber-elastic material in which the particles responsible for the electrical conductivity are embedded. The electrically conductive particles are more particularly metal particles or metallized plastic particles.
During the manufacture of the piezoelectric valve the elastic plug in the form of a prefabricated elastic body may be inserted into the respective cutout. More particularly as regards optimum sealing it is however considered to be more advantageous for the elastic plug to be formed by the introduction of liquid or pasty material into the cutout which is then cured to produce the desired rubber-elastic properties. In this case the elastic material can make optimum snug contact with the wall face of the cutout in the support body.
An optimum allowance for manufacturing inaccuracies can be expected if, for making contact with the associated contact face, the elastic plug possesses a contacting head projecting past the support body. This contact head like a contact bump will preferably possess a cross section which is large in comparison with the cutout so that it straddles or overlaps the support body in an interlocking manner at the edge of the cutout. This is responsible for an additional interlocking attachment of the elastic plug to resist high pressures occurring in the interior of the valve.
Together with at least parts of the wiring arrangement the support body is preferably fashioned as a molded interconnect device (MID). In this connection there is then the advantageous possibility of providing the wiring arrangement with electrical lines, which are formed as printed wiring structures on the support body using hot embossing technology.
There has in connection with valves admittedly already been a suggestion to resort to MID""s. Thus for instance the German: patent publication 19722925 C1 discloses a connection element for electromagnets of valve units and having a support body, through which several vias extend from one side to the other. The vias are however in this case constituted by conventional printed wiring, which must be produced in an involved wet electroplating operation. Furthermore, the German patent publication 199212659 A1 discloses a micro-valve arrangement with an integrated wiring support, which possesses electrical conductors and furthermore electronic components. The wiring arrangement is however located in the interior of valve housing of the micro-valve arrangement and furthermore there are no vias in the form of rubber-elastic bodies.
An optimum electrical connection between the elastic plug and the electrical lines of the wiring arrangement is produced if the printed wiring structure possesses a via passage aligned with the associated cutout, such passage being defined by bent over sections of the printed wiring structure and a contact bump or projection like a spigot extending coaxially into the cutout, such bump having the electrically conductive elastic plug extending through it. The contact making bump may be produce in an extremely simple manner by piercing the printed wiring structure covering over the cutout, sections of the printed wiring structure being bent over inward into the cutout and preferably coming to rest on the wall of the cutout.
Further advantageous developments and convenient forms of the invention will be understood from the following detailed descriptive disclosure of one embodiment thereof in conjunction with the accompanying drawings.